[pytrainer] Pushed amd64 stabilisation back 60 days

Waiting for upstream stabilisation of pywebkitgtk and sqlachemy-migrate.
[rstctl] Fix amd64 stabilisation date
Merge branch 'feat/amd64_keywording'

* feat/amd64_keywording:
  [rstctl] Fix amd64 stabilisation date
  [pytrainer] Pushed amd64 stabilisation back 60 days